Well, there is mental fatigue after a prolonged period without being 'out', a break. It numbs the mind. It happens in all sports, writers have it, scientists have it, .... So, to get Mata from burning out - he should have a long enough period away from football. Burnout in football is a phenomenon that for example got the attention of AC milan lab, Ajax in their youth system, and pretty much everyone that does evidence based sports development in top sports.